It is understood that there are vehicle navigation system which guide the driver of a vehicle from a current position to a destination along a calculated route, using displayed or verbal navigation instructions. The route calculation takes place regularly, in this instance, for the purpose of optimizing the route with respect to at least one optimization criterion, such as the fastest or the shortest route.
A navigation system for a land vehicle is discussed in DE 40 08 460 A1, which receives and continuously evaluates traffic messages, and calculates a first travel route without taking into account traffic messages and calculates a second traffic route while taking into account the traffic messages received. If a comparison of the first and the second route shows that the second route is probably faster than the first route, the second route is supplied as route information to an output device of the navigation system, and the driver of the land vehicle is guided to the destination on the second route.
In this procedure, which is also designated as automatic dynamization below, at each change in the traffic position an alternative route is calculated, and the additional route guidance takes place automatically, based on the new route.
A navigation system is known from Patent Abstracts of Japan, Publication Number 07-083685, in which, in addition, the second route is output as an alternative route to the first route, and the selection between the first and the second route is left to the driver.
In this version, designated also as manual dynamization below, the driver is informed on each change in the traffic situation and actively has to decide for the old or the new traffic situation and the route resulting from this. In some systems, he can also do this in the light of the routes themselves.
The two forms of the dynamization described have both specific advantages and also have disadvantages.
As one decisive advantage of automatic dynamization one might point out that the driver is not distracted unnecessarily by the navigation system, and is able to concentrate fully and completely on the road traffic. The disadvantage is that the driver is hardly able to exert personal influence. The alternative route is thus used even when it brings with it no significant route advantage compared to the old route, or the traffic message source (e.g. RDS-TMC, TMCPro or XM-TMC) is graded as being less reliable.
In manual dynamization, there is an advantage to the driver, because of the possibility of actively exerting an influence by using the old or the alternative route for the further route guidance, depending on the subjective estimation of the route change. The disadvantage is that, for each change in the traffic message position, the vehicle's driver is drawn actively into the route selection, and is thereby diverted from his real task, the active participation in the road traffic.
Consequently, the advantage of the one method is the disadvantage of the other method. On the one hand, both advantages are very agreeable to the user, but on the other hand, the two disadvantages are definitely problematic.
A variant of manual dynamization is discussed in EP 0 838 797 B1, which eases the selection of the route by the user to the extent that route guidance instructions are offered to him, and one of the two routes is selected by following one of the route guidance instructions, that is, by conclusory action.